Allow packages from "symfony/*" ^7

[phansys]

Subject

I am targeting this branch, because this change respects BC.

Changelog

### Added
- Support for packages from `symfony/*` 7.x

To do

• [x] Wait for the resolution in shivammathur/setup-php#799.

~~I don't know why we need to disable the "psr" extension for the "composer" CI job in this repository, so I left this change in a separated commit. Please, let me know if you have any concern or insight about this.~~

[VincentLanglet]

Thanks